The present invention relates, in general, to a crash box for a motor vehicle.
Nothing in the following discussion of the state of the art is to be construed as an admission of prior art.
Crash boxes are thin-walled, typically rectangular elements of steel, aluminum, or plastic, and disposed between a bumper cross member and a longitudinal member of a motor vehicle, for preventing damage to the vehicle body in the event of frontal or rear-end collisions at low speed. Crash boxes can be manufactured by joining compressed sheet-metal shells, or in single-piece construction using an extruded aluminum section for example. In the event of an impact, the crash box converts the generated kinetic energy into deformation work to prevent permanent damage to the longitudinal member when a critical stress level has been exceeded.
Crash boxes may be secured to the longitudinal members by means of flanged plates mounted to the end surface of the longitudinal members. This approach is disadvantageous because of the need for additional components, i.e. flanged plates, so that the overall weight of the motor vehicle is increased. The installation space between the longitudinal members is however critical for the installation of the drive unit. Flanged plates reduce the necessary installation space and complicate the installation. In addition, the use of flanged plates requires also room for tools which oftentimes is not available to allow installation of an optimum construction.
Another approach is disclosed in German utility model no. DE 298 08 143 U1, which describes a securement of crash boxes on the side to the longitudinal members by means of transverse bolts extending through the longitudinal members. Like the afore-described support of the crash boxes on the end surface of the longitudinal members, this construction too requires increased installation space.
Insertion of crash boxes into the longitudinal members has also been proposed in order to attempt a better utilization of the available installation space within the longitudinal members. Examples include International Publication Number WO 99/15364 or U.S. Pat. No. 3,633,934 which disclose telescoping dampers that slide into the longitudinal members in the event of a collision. German Offenlegungsschrift DE 42 38 631 A1 describes a damper having inner and outer tubes which move within one another, with the outer tube being supported on the longitudinal member by a flange.
It would be desirable and advantageous to provide an improved crash box which obviates prior art shortcomings and which requires little space and is easy to secure to the longitudinal beam while having a lightweight structure and allowing a tolerance compensation between the crash box and the longitudinal member.